In certain situations, such as in the use of medical devices, operators (who often have low margin for error) develop certain preferences for how the control panel of a device is organized. These preferences pertain, for example, to whether a certain function is controlled using the left or right hands, as well as what type of control device is used to effect such control. Designers typically solve the left/right hand dichotomy by positioning “hand sensitive” switches as close to the center-line as possible. This, of course, is not always practical and even when controls are placed on or near the center of the device such a compromise is not fully satisfactory to any of the users.
An even more difficult problem to solve is the choice of switch type for a particular function. Some users may, for example, prefer slider switches while others desire rotary controls for the same function. The designer can only satisfy one of these user's preferences.
When a control type becomes obsolete, either because a newer control works better or because the function is no longer required, it is necessary to redesign the control panel and upgrade the device even though the hardware within the device has not changed. This is a costly and time-consuming problem and adds cost to the consumer. In the field of medical devices, as well as in other fields of endeavor, such costs need to be controlled.